Does a limit on how many you can buy make you buy more?

A while back, I teamed up with two professor friends of mine—Steve Hoch and Bob Kent—to see if anchoring influences how much food we buy in grocery stores. We believed that grocery shoppers who saw numerical signs such as “Limit 12 Per Person” would buy much more than those who saw signs such as “No Limit Per Person.” To nail down the psychology behind this, we repeated this study in different forms, using different numbers, different promotions (like “2 for $2” versus “1 for $1”), and in different supermarkets and convenience stores. By the time we finished, we knew that almost any sign with a number promotion leads us to buy 30 to 100 percent more than we normally would.

Need more proof?

After the research was completed and published in the Journal of Marketing Research, another friend and I were in the checkout line at a grocery store, where I saw a sign advertising gum, “10 packs for $2.” I was eagerly counting out 10 packs onto the conveyer belt, when my friend commented, “Didn’t you just publish a big research paper on that?”